1. Field of the Invention
The present invention relates to a fan motor drive control apparatus for controlling the drive of a fan motor used as a cooling unit in an information-process equipment, an electric appliance, a vehicle or the like, and in particular to a fan motor drive control apparatus which can enhance the reliability of an air cooling function.
2. Description of the Related Art
In order to constrain harmful thermal effects in an equipment having a heat source in its housing, such as an information-processing equipment, an electric appliance or a vehicle incorporating an engine, there have been conventionally used configurations that a cooling fan motor is driven for cooling the equipment. There have been motor drive systems of various type, that is, a non-control system in which a fan motor is driven with a constant voltage in order to obtain a constant air volume, a temperature sensing system in which a temperature of a heat source is detected in order to obtain an air volume depending upon the detected temperature during operation of a fan motor.
These years, the performance and the function of the information processing equipment have been increased so that heat generation in electronic components incorporated therein has been increased, and accordingly, efficient air cooling has been increasingly important. For example, a server as a host computer or the like, incorporates a plurality of CPUs, memories and the like in order to materialize high dense packaging and speed-up operation, and accordingly, several fan motors are incorporated in order to enhance the air-cooling efficiency thereof.
Incidentally, in such a case that some of the incorporated fan motors fails so as to come to a stop, the air cooling efficiency is lowered, possibly resulting in occurrence of thermal runaway, and accordingly, readout of electronic data would become impossible at worst. Thus, for failure detection in such a case that a fan motor fails, a speed of the fan motor, a constraint protection signal and the like can be obtained from the fan motor. Thus, these signals are analyzed on the server side in order to find out which one of the fan motors fails so as to come to a stop.
For example, a patent document 1, the Japanese Utility Model Laid-Open No. H05-2570 (FIG. 1) discloses a dual cooling fan unit in which a stand-by motor has been previously prepared for a failure of a motor, and when a failure and stopping of a main fan motor are detected on the server side, the operation is changed over onto the stand-by motor in accordance with a predetermined signal delivered from the fan motor side in order to prevent lowering of the cooling function and an occurrence of thermal runaway.
However, the above-mentioned contrivance disclosed in the above-mentioned patent document 1 offers the following problems in such a case that the two fan motors both have a main-main relationship and not a main and standby relationship.
That is, in order to enhance the cooling efficiency, for example, two fan motors which are incorporated in the server as a host computer are both operated simultaneously. In this case, when one of the fan motors fails and comes to a stop, the air volume is decreased, of course, to a half. On the server side, this failure and stopping of the motor is detected in view of a predetermined signal, as stated above, but the air volume cannot be recovered from the half value unless the failed motor is artificially replaced with new one. As a result, the cooling performance is lowered so that heat radiation from electronic components in the server is insufficient, and accordingly, there would be caused occurrence of thermal runaway and impossible readout of electronic data.
In view of this point, it is contrivable that if a failure and stopping of one of motors is detected on the server side, the speed of the other normal fan motor is increased in order to ensure a sufficient air volume and pressure. However, a fan motor has not, in general, such a function that the speed thereof is spontaneously increased by the motor itself, and accordingly, in this case, an additional function is required on the server side, resulting in unavoidable complication and increased costs.